Isoprenoids are isoprene polymers that find use in pharmaceuticals, neutraceuticals, flavors, fragrances, and rubber products. Supplies of natural isoprenoid, however, are restricted due to ecological concerns. For this reason, and in order to provide isoprenoid compositions having less impurities and greater uniformity, isoprenoids such as rubber are often produced synthetically. Isoprene (2-methyl-1,3-butadiene) is a volatile hydrocarbon that is insoluble in water and soluble in alcohol. Commercially viable quantities of isoprene can be obtained by direct isolation from petroleum C5 cracking fractions or by dehydration of C5 isoalkanes or isoalkenes (Weissermel and Arpe, Industrial Organic Chemistry, 4th ed., Wiley-VCH, pp. 117-122, 2003). The C5 skeleton can also be synthesized from smaller subunits.
It would be desirable, however, to have a commercially viable method of producing isoprene that was independent of nonrenewable resources. Biosynthetic production of isoprene occurs by two distinct metabolic pathways (Julsing et al., Appl Microbiol Biotechnol, 75:1377-1384, 2007). In eukaryotes and archae, isoprene is formed via the mevalonate (MVA) pathway, while some eubacteria and higher plants produce isoprene via the methylerythritol phosphate (MEP) pathway. Isoprene emissions from plants are light and temperature-dependent and increase with the association to leaf development.
An isoprene-producing enzyme, isoprene synthase, has been identified in Aspen trees (Silver and Fall, Plant Physiol, 97:1588-1591, 1991; and Silver and Fall, J Biol Chem, 270:13010-13016, 1995) and is believed to be responsible for the in vivo production of isoprene from whole leaves. Bacterial production of isoprene has also been described (Kuzma et al., Curr Microbiol, 30:97-103, 1995; and Wilkins, Chemosphere, 32:1427-1434, 1996), and it varies in amount according to the phase of bacterial growth and the nutrient content of the culture medium (U.S. Pat. No. 5,849,970 to Fall et al.; and Wagner et al., J Bacteriol, 181:4700-4703, 1999).
The levels of isoprene obtainable through bacterial systems of the prior art, however, are insufficient for commercial uses. Thus, what the art needs is an effective and large scaled bacterial or microbial isoprene production process to provide feedstock for the manufacture of isoprene.
Accordingly, as a result of an effort for developing a method of preparing isoprene using a novel isoprene synthase gene having excellent isoprene productivity, the present inventors performed mining on a novel isoprene synthase gene, and confirmed that a recombinant microorganism transformed with the isoprene synthase gene has more excellent isoprene productivity than that of a host cell transformed with the isoprene synthase gene known in the art, thereby completing the present invention.